1. Field of the Invention
The present invention relates to a discharging element substrate, a printhead, and a printing apparatus.
2. Description of the Related Art
An inkjet printing apparatus includes a printhead which executes printing on a printing medium. The printhead includes a discharging element substrate. The discharging element substrate has a discharging element and a driving transistor for driving the discharging element. The first voltage for energizing the discharging element and the second voltage for controlling the driving transistor are supplied separately. With this arrangement, even if potential fluctuations occur in a power supply node of the first voltage by executing printing, it is possible to reduce an influence on a printing characteristic caused by the potential fluctuations.
When, for example, the printhead is not mounted on the printing apparatus appropriately or a malfunction occurs in the printing apparatus, a situation in which the second voltage out of a plurality of voltages including the above-described first and second voltages is not supplied may occur. A power supply node for supplying the second voltage in this case is indefinite (for example, 0 [V]).
If the voltage of the power supply node supplying the second voltage becomes, for example, 0 [V], an overvoltage may be generated between the source and the gate of the above-described driving transistor. This may cause the insulation breakdown of the driving transistor.